Airbag suspension system for articulated combine

ABSTRACT

The present invention is directed to an airbag suspension system for a vehicle. The airbag suspension system includes a vehicle frame having an axle to which is affixed a longitudinal beam carrying at least one wheel. The airbag assembly of the suspension system includes an upper plate extending from the vehicle frame and a lower plate affixed to the longitudinal beam. Disposed between the upper and lower plates is an airbag. The lower plate carries a pair of vertical blocks having vertical slots, a pair of cams being carried by the upper plate and riding in the vertical slots. The airbag suspension system may be used with a vehicle such as an articulated combine, that rides on a pair of wheeled tires or on a pair of endless tracks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No.09/575,519, filed May 22, 2000, now U.S. Pat. No. 6,339,917; which is acontinuation-in-part of application Ser. No. 09/481,046, filed Jan. 11,2000, now U.S. Pat. No. 6,125,618; which is a divisional application ofapplication Ser. No. 09/040,985, filed Mar. 18, 1998, now U.S. Pat. No.6,012,272; and is cross referenced to application Ser. No. 09/210,331,filed Dec. 11, 1998, now U.S. Pat. No. 6,167,982.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

The present invention generally relates to combines and moreparticularly to an articulated (jointed) combine which employs, interalia, an improved joint, unloading capability, grain transfercapability, airbag suspension, straw and chaff conveyor,suspended/movable fuel tank, control/steering, and extremely large grainstorage capacity.

A modem agricultural combine typically unloads or transfers clean grainfrom its on-board storage hopper utilizing an auger of fixed lengthwhich swings out in a fixed radius and fixed elevation arc from itsstowed position. The stowed position generally is pointing to the rearof the combine. The auger in turn generally is driven by a mechanicalarrangement of belts, chains, clutch, and gearbox. The unload auger inmost combine designs swings out to the operator's left. The auger lengthgenerally is limited by the practical distance that it can extend beyondthe rear of the combine in its stowed position without creating aserious maneuvering hazard.

As the size of on-board storage hoppers and capacity of combines hasincreased, the time required to maneuver the machine next to the grainreceiving wagon or truck and the grain transfer time have become a majorcomponent of the total harvesting time. Conventional combines have agrain hopper capacity of 250 to 300 bushels and unload auger capacitiesof 1.9 to 2.6 bushels per second.

The unload time of the hopper typically is about 2 to 3 minutes with theunload auger running at maximum speed and 1 to 2 minutes are taken tomaneuver the combine into the optimum unload position next to the truckor wagon. Re-positioning the combine and running the auger at less thanmaximum speed are often encountered when topping off the truck or wagonwhich is receiving the grain. As modem combine harvesting capacitiesapproach 3,000 bushes per hour, the unload cycle must be repeated every8 to 10 minutes. Therefore, the total unload time or non-harvesting timeis a significant reduction of total grain harvesting productivity. Agrain capacity of about 600-650 bushels would permit the combine toharvest for about 1 mile, which would greatly reduce unloading cycles.

This productivity loss can be countered by a second operator utilizing atractor and grain cart following the combine back and forth through thefield to unload the on-board combine storage hopper without stopping theharvesting process. Alternatively, a combine with an integrated graincart, as disclosed in applicant's U.S. Pat. No. 5,904,365 can beutilized to reduce the number of unload cycles and at least double therate at which grain is discharged to the receiving vehicle.

Unloading combines into semi-trailer road trucks has become theprevalent practice as opposed to field wagons that were utilized in thepast. These road trucks typically are parked at the side of the road andnot in the field where the combine is operating. This necessary practicealmost always creates an elevational difference between the twovehicles. These road trucks themselves also have widely varying heights.These two conditions create a big variation in the optimum elevation ofthe discharge point of the combine unloading system. Combinemanufacturers have attempted to address this problem with ever-longeraugers and higher fixed swing out arcs. There are, however, limits toboth. This fixed point discharge point frequently ends up too high, toolow, too far from the combine, or too close to the combine for optimumtruck loading conditions. Such conditions require repositioning thecombine with respect to the vehicle while it is unloading.

Existing combine unloading systems can unload from one side of themachine only. This frequently requires 180° turns by the combine toposition it on the proper side to unload the grain into the road truck.It also means that while harvesting the combine generally only can beunloaded into a moving grain cart only while traveling along theleft-hand side of the unharvested crop since access to the unloaderwould be precluded by the unharvested crop were the combine to belocated to the right of the crop.

When topping off or completely filling the truck or wagon, it isnecessary for the operator to inch the combine forward or backwardduring the process. In addition to being cumbersome, the combine must bepositioned close to perfectly parallel to the receiving vehicle or astop and reposition is necessary. Moving the auger through its fixed arcfrequently cannot solve the lack of parallel orientation.

An agricultural combine has multiple steering requirements. Precisecontrol is needed as the row harvesting units such as a cornhead, areguided through the rows of grain. When the end of the field is reached,a tight turning radius is needed to proceed back across the field inorder to harvest the crop immediately adjacent to the just-completedrows or round. Concomitant with its field performance, this largevehicle also must be controlled on the roadway at speeds of around 20mph and around tight corners. Another steering associated problem is toturn multiple axle, heavily-loaded bogies with large tires in a tightradius while minimizing sliding the tires in the horizontal(particularly in the lateral) direction, which places high stresses inthe suspension, piles up dirt in the field, and causes excessive tirewear.

Early attempts at an articulated combine are reported in U.S. Pat. Nos.4,317,326 and 4,414,794. The design capacity is stated to be around 360bushels. Its unloading mechanism is limited to one side of the combineand steering is accomplished only by articulation steering cylinders.U.S. Pat. No. 4,453,614 proposes a steering cylinder arrangement for anarticulated combine. U.S. Pat. No. 4,204,386 proposes an articulatedmachine for gathering vegetables. U.S. Pat. No. 5,857,907 proposes adischarge conveyor having a secondary, variably extending conveyorattached to the terminal end of the discharge conveyor.

U.S. Pat. No. 6,012,272 (the '272 patent) discloses an articulatedcombine composed of a forward unit or bogey having an operator's cab,engine, grain harvesting assembly, grain transfer assembly, but noon-board grain storage; and a rear unit or bogey jointedly attached tothe forward unit and having a steerable and powered wheel assembly, anon-board grain storage bin, and a grain off-loading assembly. Many ofthe industry long-felt, but unsolved needs regarding articulatedcombines are disclosed in the '272 patent. Basic improvements theretoare the subject of this application.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a combine having increasedon-board grain storage capacity. The combine includes a forward unithaving an operator's cab, an engine, a grain harvesting assembly, agrain transfer assembly, and is devoid of an on-board grain bin. Thecombine also has a rearward unit jointedly attached to the forwardsection. The rearward unit has a powered wheel assembly, an onboardgrain bin for receiving grain from the forward section grain transferassembly, and a grain off-loading assembly.

Another aspect of the present invention is directed to a joint for apowered articulated vehicle, such as a combine for joining a forwardunit to a rearward unit. The joint includes an upper frame membercarried by the forward unit and having a recess on its lower side and alower frame member carried by the forward unit, having a recess on itsupper side, and being spaced-apart vertically below the upper framemember so that the recesses are in vertical registration. The jointfurther includes a shaft carried by the rearward unit and a bearingretainer assembly carried by the end of the shaft and disposed betweenthe recesses. The bearing assembly includes an outer annulus surmountingan inner hub which hub is connected to the shaft with thrust bearingsinserted between the annulus and said hub, whereby the inner hubco-rotates with shaft with respect to the outer annulus. The bearingassembly also includes a pair of nibs carried by the outer annulus whichnibs reside in the upper and lower recesses and which nibs areassociated with tapered roller bearings so that the outer annulusco-twists with the shaft respect to the forward unit. Uniquely, thejoint is stiff in the vertical plane through the longitudinal axisformed along the forward unit frame members and the rear unit shaft,i.e., around the pitch axis. It will be appreciated that the upper andlower frame members could be carried by the rearward unit and the shaftcarried by the forward unit and the novel joint would function the sameas with the configuration set forth above.

A further aspect of the present invention is an improved articulatedcombine comprising a forward unit connected by a joint to a rearwardunit. The improvement for transferring clean grain from the forward unitto the rearward unit includes the rearward unit carrying an onboardgrain bin and having a front wall that has a horizontal slot therein.The front wall retains a horizontally elongate grain transfer troughaffixed thereto which trough is curved with its center of curvaturecongruent with the center of articulation of the combine. The trough isin communication with the bin via the slot. The forward unit carries agrain transfer assembly of a fixed elongate discharge chute that emptiesinto the rearward unit trough while the forward and rearward units arebeing turned about the joint.

A still further aspect of the present invention is a grain unloadingassembly for unloading clean grain from a combine grain bin, wherein acombine harvests grain and cleans it to provide the clean grain. Suchgrain unloading assembly includes a vertical flighted conveyor that isadapted to operate in either direction. Also included is a housing inwhich the vertical flighted conveyor is disposed. The housing is fittedat its top with a bin spout, a discharge spout, a moveable door thatpermits communication of the flighted conveyor either with the bin spoutor with the discharge spout. A first opening at the bottom of thehousing is covered with a moveable door for permitting grain in the binto be moved into the housing for conveying by the flighted conveyor. Asecond opening at its bottom of the housing is for permitting cleangrain to be passed into the housing from the combine.

Yet another aspect of the present invention is an unload assembly forunloading clean grain from a combine grain bin. This unload assemblyincludes a distal frame nested within a proximal frame. The distal frameis extensible from and retractable into the proximal frame. The distalframe has a discharge end for discharging grain. The proximal frame hasa feed end for receiving grain from the grain bin and a distal end fromwhich the nested distal frame extends and retracts. This unload assemblyfurther includes a conveyor system that includes a first fixed pulleylocated at the feed end of the proximal frame. A second fixed pulley islocated at the discharge end of the distal frame. A third fixed pulleyis located at the distal end of the proximal frame. A fourth moveablepulley is disposed within the proximal frame intermediate the first andthird fixed pulleys. The conveyor extends from the first pulley to thesecond pulley to the fourth pulley to the third pulley and back to thefirst pulley. A fifth pulley may be employed near the first pulley toincrease the wrap angle of the conveyor belt around the first pulley.This arrangement permits the conveyor to extend as the distal conveyorextends and retracts as the distal conveyor retracts by movement of thefourth pulley.

Still a yet further aspect of the present invention is a straw and chaffspreader for mounting in association with a grain cleaner of a combine.This spreader includes a pair of generally horizontally-disposed,outwardly rotating, cleated conveyors disposed to receive straw andchaff discharged from the grain separator and cleaner of a combine.

A yet further aspect of the present invention is an airbag suspensionfor a vehicle having a vehicle frame having an axle (stub or throughaxle) extending therefrom. A longitudinal beam is affixed to the axlethat carries at least one wheel. An airbag assembly includes an upperplate extending from the vehicle frame, a lower plate affixed to thelongitudinal beam, and an airbag disposed between the upper and lowerplates. The lower plate carries a pair of vertical blocks havingvertical slots. A pair of cams is carried by the upper plate and ridesin the vertical slots.

Another aspect of the present invention is a steering system for anarticulated vehicle having a joint that connects a forward unit and arearward unit and at least one articulation cylinder to provide aturning force at the joint. The steering system includes an operatorspeed and direction mechanism whereby an operator can direct the desireddirection of the vehicle. A power source is provided for driving pumpsadapted to drive motors and cylinders. The forward unit has tractivewheels (tired or tracked) powered by one or more motors. Each motor hasa transducer for measuring its rotational speed and direction. Therearward unit has a pair of tractive endless tracks or tired wheels eachpowered by a separate motor. Each motor has a transducer for measuringits rotational speed. A programmable controller receives the rotationalspeed measurements (for over-speed control) and pressures from all ofthe transducers and operator steering commands from the speed anddirection mechanism, and responds with suitable outputs. Actuatorsreceive the controller outputs and adjust the output of each of themotors powering the rearward unit tracks/wheels.

A still further aspect of the present invention is an improved combinehaving a fuel tank, and which includes an overhead rail from which thefuel tank is suspended and an optional actuator connected to the fueltank for moving the fuel tank forwardly and rearwardly. Desirably,though, the fuel tank can be moved forwardly and rearwardly by hand.

A still further aspect of the present invention is a method forarticulating an articulated vehicle at a rest position wherein thevehicle is composed of a forward unit and a tracked rearward unit havinga pair of powered tracks. The forward and rearward units are connectedby a joint and an articulation cylinder. The method powers up only onetrack while simultaneously actuating the articulation cylinder.

Advantages of the present invention include a combine design, preferablyan articulated combine, which enables grain storage capacity of between500 and 1,000 bushels or more. Another advantage is an articulatedcombine which can unload clean grain to either side and which iscontrolled by a unique control system. A further advantage is a uniquesteering system for an articulated combine. These and other advantageswill be readily apparent to those skilled in this art.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the presentinvention, reference should be had to the following detailed descriptiontaken in connection with the accompanying drawings in which:

FIG. 1 is a side elevational view of the novel combine (or harvester)with, inter alia, extra large storage capacity, straw and chaffconveyor, novel joint, clean grain transfer ability, and unloadingcapacity;

FIG. 2 is a side elevational view of the other side of the novel combinedepicted in FIG. 1, fitted with caster wheels at the rear of the frontunit;

FIG. 3 is an overhead view of the combine depicted in FIG. 1;

FIG. 4 is a rear view of the rear unit of the combine depicted in FIG.1;

FIG. 5 is a sectional view taken along line 5—5 of FIG. 1;

FIG. 6 is a sectional view taken along line 6—6 of FIG. 5 showing a planview in greater detail of joint 22;

FIG. 7 is a sectional view taken along line 7—7 of FIG. 6;

FIG. 8 is a sectional view like that taken along line 7—7, but of apreferred embodiment of the joint of FIG. 6;

FIG. 9 is a sectional view taken along line 9—9 of FIG. 8;

FIG. 10 is an overhead view of the straw and chaff conveyor systemfitted at the rear of the front unit of the novel combine;

FIG. 11 is a side cut-away view of the rear unit of the novel combineshowing the grain transfer system between the front and rear units andthe grain handling system aboard the rear grain bin unit;

FIG. 12 is a rear cut-away view of the rear unit of the novel combineshowing part of the grain handling system aboard the rear grain binunit;

FIG. 13 is a side cut-away view of the hydraulic nested grainoff-loading assembly in its retracted position;

FIG. 14 is a side cut-away view of the hydraulic nested grainoff-loading assembly in its extended position;

FIG. 15 is a partial side elevational view of a joystick used to controlthe clean grain transfer assembly depicted in FIGS. 13 and 14;

FIG. 16 is a top view of the joystick shown in FIG. 15;

FIG. 17 is a schematic of the hydraulic vertical control for the cleangrain transfer assembly of FIGS. 13 and 14;

FIG. 18 is a schematic of the hydraulic swing control for the cleangrain transfer assembly of FIGS. 13 and 14;

FIG. 19 is a schematic of the hydraulic telescoping control for theclean grain transfer assembly of FIGS. 13 and 14;

FIG. 20 is a schematic of the hydraulic speed control for the cleangrain transfer assembly of FIGS. 13 and 14;

FIG. 21 is a side elevational view of the novel suspension system of therear grain bin unit;

FIG. 22 is a sectional view taken along line 22—22 of FIG. 15;

FIG. 23 is a sectional view taken along line 21—21 of FIG. 15;

FIG. 24 is a side elevational view of a combine like that depicted inFIG. 1, except that the rear unit is wheeled rather than fitted with anendless track;

FIG. 25 is a rear elevational view of the combine in FIG. 24;

FIG. 26 is an overhead view of the combine in FIG. 24;

FIG. 27 is a partial sectional view of the suspension system of thecombine in FIG. 24;

FIG. 28 is a simplified overhead schematic of the turning geometry for awheeled rear unit embodiment of the present invention; and

FIG. 29 is a schematic of the hydraulic steering system for the novelarticulated combine.

The drawings will be described in detail below.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides basic improvements to the '272 patentarticulated combine, which disclosed solutions to many problemsassociated with modem farming combines by providing a harvester that canunload readily on either side and to virtually any height road truck.The disclosed harvester retains the increased capacity of harvestedgrain carrying capacity from about 200-300 bushels in conventionalcombines to about 500-1,200 bushels utilizing the rearward-only grainbin, because the rearward unit has more capacity (space) than there isin a grain bin located over a front axle. This is important because thecapacity of a typical road semi-trailer is 1,000 bushels. This meansthat the disclosed combine can fill an entire road truck from itson-board grain bin in a single unloading. Moreover, a unique, unloadingsystem permits unloading of clean grain from the rearward grain bin unitout to either side of the combine. Such increased grain storage capacityis possible because the grain bin is located on the rearward unit, whichpermits a much lower center of gravity to be designed into the rearwardunit.

In order to ensure that the extra weight can be easily maneuvered by thenovel harvester, the rearward unit has powered and steerable wheels thatare supported by a unique airbag suspension system. A new clean graintransfer assembly for transferring clean grain from the forward unit tothe rearward cart bin unit also is disclosed. An improved two-axis jointinterconnects the forward and rearward units. Straw and chaff from theharvesting assembly is discharged to either side by a unique dualconveyor system. “Wheels” or “wheeled” for present purposes includesboth wheels that are fitted with tires (pneumatic tires) and wheels thatare fitted with endless tracks.

Referring initially to FIGS. 1, 2 and 3, innovative combine 10 generallyincludes forward unit 12 and rearward unit 14. Forward unit 12 is seento include cab 15 in which the operator is seated, cornhead or smallgrainhead 16, engine compartment 18 (two cooling fan air inlets shown inthe drawings), and powered non-steerable wheel pair 20. In thealternative embodiment in FIG. 2, forward unit 12 is fitted with casterwheel pair 19 located at the rear of forward unit 12. Rearward unit 14is interconnected to forward unit 12 via joint assembly 22 and cleangrain is transferred from forward unit 12 to rearward unit 14 via cleangrain transfer assembly 24. Rearward unit 14 is seen to include cleangrain unloading system 26 in its stored position and in phantom in twopossible raised unloading positions in FIG. 3, grain bin 28, and poweredendless tracks 30 and 32. Use of a dual track system supporting grainbin 28 on rearward unit 14 contributes to the capability of grain bin 28holding upwards to 1,200 bushels of grain. Providing the grain bincapacity only on rearward unit 14 translates into a lower center ofgravity for grain bin 28 which also enables such higher storage capacityand provides more even weight distribution per axle. Importantly, atabout 600-650 bushel capacity of grain bin 28, combine 10 could harvest,for example, a cornfield for one mile before unloading. Capacity inexcess of requirement means that combine 10 can harvest for even greaterdistances before unloading.

As seen in FIG. 2, fuel tank 34 is carried suspended by rail 36 and ismoveable from a forward to a rearward position as indicated by arrow 38.Movement of suspended fuel tank 34 ensures access to, for example,hydraulic lines and other components should such access be necessary,desirable, or convenient. Such fuel tank movement also enables weightshifting of forward unit 12, should such weight shifting also benecessary, desirable, or convenient.

As seen in FIG. 4, grain bin 28 is fitted with ladder 40 for operatoraccess to the interior of grain bin 28. Grain bin 28 also is fitted apair of light arrays, 42 and 44, as the combine may traverse roadways inorder to access field to harvest. Other items of interest in this rearview of the combine will be discussed later in connection with otherfeatures of the novel articulated combine.

Referring to FIGS. 5, 6 and 7 that illustrate joint 22, initially, itwill be observed that a pair of steering cylinders, 46 and 48, are seenin FIG. 5 to connect forward unit 12 to rearward unit 14 of articulatedcombine 10. Such steering cylinders are conventionally used to assist inthe steering of articulated vehicles and are provided here for suchsteering use in the present articulated combine design. Now, withrespect to the two-axis joint, pipe 50 is attached to rearward unit 14at one end and is constructed as a round pipe or structural tube. Shaft52 extends from pipe 50 towards forward unit 12 and is inserted intobearing retainer assembly 60 which is inserted between upper framemember 54 and lower frame member 56. These frame members 54 and 56 arebolted to forward unit 12 via bolts 58 a-d; although, other attachmentmeans certainly can be envisioned. Each frame member 54 and 56 has aninner recess that confronts the corresponding recess in the other andinto which is inserted bearing retainer assembly 60.

Bearing retainer assembly 60 has a pair of nibs or ears which fit intoframe member 54 and 56 recesses and which ride on tapered roller bearing62 a-62 b to provide sideways movement to units 12 and 14 via pipe 50.Such sideways movement permits combine 10 to be steered. A holepenetrates through bearing retainer assembly 60 into which areduced-diameter threaded end of shaft 52 fits and is secured via nut64. Now, thrust bearings 66 and 68 fit into counterbores that adjoin thehole through bearing retainer assembly 60 and which thrust bearingspermit shaft 52 to rotate and which, thus, enables units 12 and 14 torotate with respect to each other. Such rotation permits units 12 and 14to traverse uneven terrain during harvesting or other movement ofcombine 10. Note, however, that pipe 50 and shaft 52 are not permittedto move in a vertical direction due to the unique construction of jointassembly 22. Thus, a unique dual axis joint has been disclosed. Itshould be understood that the connection of joint 22 could be thereverse of that connection depicted in FIGS. 5, 6, and 7. That is, pipe50 could be attached to forward unit 12 rather than rearward unit 14.

A modified version of the joint depicted in FIGS. 6 and 7 has now beendesigned and is illustrated in FIGS. 8 and 9. It utilizes the featuresof joint 22 of FIGS. 6 and 7, except that additional thrust bearingshave been added to take up the additional separational forces that joint22 sees due to taped roller bearings 62 and 66. Also, the joint in FIGS.8 and 9 has been rotated 180° so shaft 52 now is connected to forwardunit 12, rather than to rearward unit 14 via pipe 50, as is shown inFIGS. 6 and 7. Also, frame members 54 and 56 are removably attached toframe member 59 that is connected to rear unit 14. Additionally, spacers51 are held in place by threaded bolts 53 and 55, which fit throughholes in frame members 54 and 56, respectively. The basic constructionof the joint in FIGS. 8 and 9 is like that for joint 22, except thatframe members 54/56 have apertures into which flanged plug assemblies 70and 72 are placed and held securely by threaded members 74 and 76,respectively. Recesses adjacent the apertures in frame members 54/56contain races into which thrust bearings 78 and 80, respectively fit andare retained by the flared heads of flanged plugs 70 and 72. Flangedplug assemblies 70 and 72 include spacers (not shown in the drawings) toensure that tapered roller bearings 62 and 66 are not excessivelypre-loaded when flanged plugs 70 and 72 are tightened and washers (notshown in the drawings) are provided for the flanges of plugs 70 and 72to bear against when tightened.

Regarding to the novel two-axis joint as disclosed in the '272 patent,unique to joint 22 is that it is a “single point” joint. That is, joint22 is designed to be only about a foot or so high. No other structuralconnection between forward unit 12 and rearward unit 14 is required bydint of the design of joint 22. That is not to say that other structuralconnection cannot be made between forward unit 12 and rearward unit 14,but that no other structural connection is necessary. In fact, it is apositive advantage that no other structural interconnection is neededbetween the two units because the combine designer has greaterflexibility in locating equipment, lines, feeders, etc. because of thesingle point joint design disclosed herein.

Referring now to FIG. 10, the description will commence with thetransfer of clean grain from forward unit 12 to grain bin 28 and will becompleted with off-loading of the grain into, e.g., a semi-truck. Inthis regard, clean grain and straw and chaff separately exit from graincleaner assembly 82 (which is quite conventional). The straw and chafffalls down onto dual conveyors 84 and 86 that are separately driven byhydraulic motors 88 and 90, respectively. Alternatively, conveyors 84and 86 could be driven by a single motor with appropriate gearing,belts, or the like, providing for the movement of the non-drivenconveyor either in the same direction or in the opposite direction fromthe driven conveyor. Conveyors 84/86 also can be seen in FIGS. 1-3 to belocated above joint assembly 22. In normal operation where combine 10 istraveling through the field harvesting grain, conveyors 84 and 86 eachrotate so as to throw the straw and chaff outwardly from combine 10.During a turn, it may be advantageous to not bunch up straw and chaffunder the rear wheels of rearward unit 14, so both conveyors can be setto throw the straw and chaff to the side of combine 10 that is oppositethe direction of the turn. Since conveyors 84/86 desirably areseparately powered, they can be rotated in the same direction or inopposite directions. Regardless of the direction of their turning,conveyors 84/86 ensure that the straw and chaff will not fall down onjoint assembly 22 nor bunch up directly underneath combine 10 forrearward unit 14 to traverse over.

The clean grain from the grain cleaning operation aboard forward unit 12travels to clean grain transfer assembly 24 (see FIGS. 1-3 and 11).Referring especially to FIG. 11, it will be observed that clean grainpasses down fixed elongate discharge chute 92 into elongate horizontaltrough 94 that is connected to the forward wall of grain bin 28. FromFIG. 3, it can be seen that the front of trough 94 is curved (orarcuate) to match the radius of curvature of articulation of combine 10.Such curvature ensures that fixed chute 92 always will empty clean graininto trough 94 even while combine 10 is turning (articulating). Nowfront wall 96 of grain bin 28 has slot 98 that permits clean grain intrough 94 to be passed to the inside (or cavity) of bin 28. The designof clean grain transfer assembly 24 is simple in that gravity is used tofeed the clean grain from forward unit 12 into trough 94 via chute 92.Gravity also ensures that the clean grain in trough 94 passes throughslot 98 into grain bin 28.

The clean grain passing through slot 98 enters vertical conveyor system100 that passes the clean grain into bin 28 and also to clean grainoff-loading assembly 26. As such, vertical conveyor assembly 100 iscentral to proper grain handling within grain bin 28. To that end,vertical conveyor system 100 includes flighted (paddled) conveyor 102disposed within housing assembly 104. Conveyor 102 is driven byhydraulic motor 106 (see FIG. 4) and its direction is reversible and itsspeed is variable. At the top of conveyor assembly 100 are a pair ofdischarge chutes, 108 and 110 (which will be described later). Moveabledoor 112 powered by hydraulic cylinder 115 (see FIG. 2) permits cleangrain to be discharged either by chute 108, chute 110 or both with thedirection of conveyor 102 being coordinated with the position of door112. With door 112 in the position shown in FIG. 11, conveyor 112 wouldbe set to rotate in the counterclockwise direction by motor 106 (thedirection of rotation is given with respect to FIG. 11, as direction ofmovement is determined by the position of the observer). Grain enteringhousing 104 via slot 98 would be discharged into grain bin 28. When door112 is moved into the dashed line position and the direction of conveyor102 reversed, grain would be discharged through chute 110 into unloadassembly 26, which will described in detail below. It is possible tounload bin 28 while harvesting as also will be described below. Due toall the grain being dumped into bin 28 through chute 110, top levelingaugers also can be provided to even out the clean grain stored in grainbin 28.

To continue with the flow of clean grain, once clean grain enters bin28, it is stored there until it is required to be discharged. Referringto FIGS. 3, 5, 11, and 12, the first step is clean grain dischargecommences with a unique floor design that includes drag paddles 114 and116 that are powered by hydraulic motor 118 (see FIG. 4) that can beaccessed via door 120 at the rear of grain bin 28. Drag paddles 114/116essentially create a fluidized bed of grain that is fed from bin 28through moveable door 122 that is powered by hydraulic cylinder 124 (seeFIG. 11) and into housing 104. It will be appreciated that augers or thelike could replace drag paddles 114/116; although, the flatness ofpaddles permits bin 28 to have a flat floor which increases the graincapacity of bin 28. In order to prevent the grain in bin 28 fromstopping the movement of drag paddles 114/116 and in order to metergrain to such drag paddles, adjustable inverted-V floor assembly 126 isstationed just above drag paddles 114/116 (see FIGS. 3 and 12). Moveabledoors or the like could substitute therefor. It will be appreciated thateach inverted-V (e.g., V 128) retains a pair of adjustable louvers(e.g., louvers 130 and 132) that can finely adjust the openings betweeneach inverted-V. Such louver arrangement provides for precise meteringof grain from bin 28 to drag paddles 114/116. Louvers 130/132 can beadjusted manually; although, hydraulic adjustment could be provided.

Now that drag paddles have pulled/pushed the clean grain into housing104, if conveyor 102 rotated in a clockwise direction with door 112actuated to the dashed line position (i.e., chute 108 closed and chute110 open), then clean grain in bin 28 will be conveyed by conveyor 102up through housing 104 and be discharged via chute 110 onto clean grainunloading system 26. Should combine 10 be harvesting field grain whileoff-loading is progressing, then not only will grain housed within grainbin 28 be off-loaded (unloaded), but so too will clean grain enteringhousing 104 via slot 98 from grain transfer system 24. Thus, the novelcombine has the capability of harvesting and unloading grainconcurrently. Once clean grain in grain bin 28 has been off-loaded, door112 is moved to its position as shown in FIG. 11 and conveyor 102reversed in its direction of travel to then throw clean grain back intobin 28.

Clean grain unloading system 26 (see FIGS. 2 and 13) includes nestedconveyor assembly 134, which includes distal frame 136 with grain chute137 nested within proximal frame 138. Housed within frames 136/138 iscleated (or flighted) endless conveyor belt 140. Nested conveyorassembly 134 rests on cradle 142 that is formed from a shaft (not seenin the drawings) and rollers, such as roller 144 (see FIG. 3). Cradle142 permits the nested conveyor assembly 134 to move along itslongitudinal axis with respect to cradle 142 when combine 10articulates. Rotational power is not supplied to conveyor assembly 134when no clean grain unloading is taking place so that it is in a floator relaxed mode; thus, permitting conveyor assembly 134 to be rotated bycradle 142 when combine 10 articulates. Chute 110 transfers clean grainthrough an aperture in proximal housing 138 directly above the pivotpoint, pivot assembly 146 (see FIGS. 13 and 14), for conveyor assembly134 so that the transfer location does not change as the conveyorrotates from side to side during unloading.

Nested conveyor assembly 134 is lifted by pistons 148 and 150, which areattached to cable 152 that runs through snatch block 154 which in turnis connected to rearward unit 14 by frame assembly 156 (see FIGS. 2 and3). Such lifting mechanism also has its pivot point in line with theaxis of rotation of conveyor assembly 134 so that conveyor assembly 134does not change height as it is rotated from side to side, such as isshown in phantom in FIG. 3. Such lifting mechanism's connection torearward unit 14 is moment decoupled to prevent conveyor assembly 134from twisting as it rotates by means of the universal attachment ofsnatch block 154 which is permitted to move in all three axes.Alternatively, rod end Heim joints could be placed at the ends of anadjustable rod in place of cable 152.

Referring to FIGS. 2, 11, 13, and 14, nested conveyor assembly 134 isrotated from side-to-side by wheel or sprocket 158 that is supported byshaft 159 for rotation of sprocket 158, a chain that encircles sprocket158 (not readily seen in the drawings), and hydraulic motor 160 whichpulls the chain through a small sprocket (also not readily seen in thedrawings). Conveyor assembly 134 is supported by pivot assembly 146,which permits conveyor assembly 134 to be inclined upwards. The centerof wheel 158 establishes both the axis of rotation and the axis ofinclination of conveyor assembly 134. Pivot assembly 146 includes ashaft disposed vertically through its center hub, which shaft issupported by an outer hub that is tied to rearward unit 14 via structure162. Additional structural stability and support (not shown in thedrawings) for wheel 158 is provided by cam follower-type rollers thatare disposed under the periphery of wheel 158 and tied to structure 162.This additional support can be helpful as the conveyor rotates whichcauses a torque load to be introduced into the center support shaft atvarious angles.

Endless conveyor 140 is driven by hydraulic motor 164 (see FIG. 2),which connects to drive pulley 166 (see FIGS. 13 and 14). From fixeddrive pulley 166, belt 140 goes to stationary pulley 168 located indistal frame 136, back to moveable pulley 170, to fixed pulley 172, toidler pulley 174, and back to drive pulley 166. Note that moveablepulley 170 is located between fixed pulleys 166 and 172. As distal frame136 is extended from proximal frame 138 by hydraulic motor 151associated with pinion 153 and rack 155, pulley 170, which otherwise isbiased inwardly, moves from a position such as is illustrated in FIG. 13to a position such as is illustrated in FIG. 14. Hydraulic motor 151 ismounted at the distal end of proximal frame 138 along with pinion 153.Rack 155 is mounted at the proximal end of distal frame 136 and isdriven by pinion 153 to extend/retract distal frame 136. Chute 137 inturn extends from its home position to an extended position so thatclean grain can be unloaded, for example, into a waiting semi-trailer.Frames 136 and 138 preferably are shrouded or covered to aid in grainretention during operation of belt 140.

With respect to operation of clean grain unloading system 26, referenceis made to FIGS. 15 and 16 which show the unique joystick control systemof the '272 patent which can be adapted to control the present unloadingsystem. Initially, joystick 200 is fitted with finger toggle switches202, 204, 206, and button 208. The operator's fingers activate toggleswitch 202 that causes unloading system 26 to move vertically up anddown. Switch 204 conveniently is thumb activated and is an on-off switchfor unloading system 26. Switch 206 is a combine inching switch; thatis, it causes combine 10 to move slowly forward or backward to placespout 137 exactly where the operator desires. Such slow movement isknown as “inching” in this field. Button 208 is a “home” button thatmeans that unloading system 26 is returned to its stored position asshown in FIG. 3, for example.

Another capability of joystick 200 is that it can move forward,backward, and laterally left and right. These movements cause unloadingsystem 26 to extend (say, forward movement of joystick 200), retract(backward movement), swing to the left (left movement), and swing to theright (right movement). Finally, joystick 200 is rotatable to controlthe speed of the belt 140 of unloading system 26.

Joystick 200 accomplishes the described movements of unloading system 26by signaling electrohydraulic valves with a signal sent to manuallyadjustable flow control valves for, say, movement of unloading system 26up/down, left/right, in/out, and home Joystick 200 signals aproportional servo valve for on/off and conveyor speed (e.g., activatesa linear electric servo that moves a pump swash plate). Joystick 200signals the propulsion system of combine 10 in order to inch the combineforward or reverse by by-passing the normal operator speed control ofthe vehicle. It should be obvious that the novel combine takes advantageof the hydraulic system already in place in conventional combines andextends their use in order to power desirably the unloading system 26and tracks 30 and 32. Other power means, of course, could be employed;however, hydraulic power tends to be more reliable.

In the unloading or off-loading mode, belt 140 always is actuated firstand turned off last in order to minimize any plugging problems. Next,the direction of vertical conveyor 102 is reversed from the grainharvesting mode and its speed is increased. Door 122 is opened and grainfed by gravity to conveyor 102 until a sensor indicates that the amountof gravity fed grain slows down. At this point, drag paddles 114/116 areactivated to feed conveyor 102.

Implementation of such joystick movements of unloading system 26 isdisplayed in FIGS. 17-19. Referring initially to FIG. 17, lines 210 and212 are connected to a source of voltage (say, 12 volts supplied by thecombine). Contacts 214 and 216 are joystick 200 contacts for raising andlowering, respectively, conveyor assembly 134 of unloading system 26.Ground 217 is provided in conventional fashion. Upon closure of one ofjoystick contacts 214 or 216, bi-directional valve with adjustable flow218 is fed hydraulic fluid at, say, 2,000 psi from a hydraulic pumpwhich feeds rod and cylinder assemblies (pistons) 148/150 via lines 220and 222 with oil returned to reservoir 224 via line 226. Assembly 134,then, raises and lowers unloading system 26 (conveyor assembly 134).

Referring to FIG. 18, lines 228 and 230 run to joystick contacts 232 and234 which actuate bi-directional valve with adjustable flow and float236 which actuates motor 160 for swinging unloading system 26 eitherleft or right. Ground 238 and return line 239 to reservoir 224 areprovided in conventional fashion. A rod and cylinder or other meanscould be substituted for motor 160.

Referring to FIG. 19, lines 240 and 242 run to joystick contacts 244 and246 which actuate bi-directional two flow valve (slow/fast speed) 248which actuates motor 151 for extending distal frame 136 from its nestedposition within frame 138. Ground 250 and return line 254 to reservoir224 are conventionally provided. A rod and cylinder or other means couldbe substituted for motor 151.

Referring to FIG. 20, the unload system speed control is shown.Specifically, combine engine 256 is connected via line 258 to pump 260,which is a variable displacement pump. Pump 258 is in fluid (oil orhydraulic fluid) communication with motor 106, which runs verticalconveyor assembly 102, via lines 262 and 264 that form a hydrostaticloop. Pump 260 is controller/actuated via joystick 200 as follows. Line266 runs through on/off switch 268 and combine speed potentiometer 270(actuated by joystick 200) to servo controller 272, which in turn isconnected via line 274 to servo actuator 276 that is connected to pump260 via line 278 for moving the swash plate of pump 260 to control thespeed and direction of vertical conveyor assembly 102 via motor 106.Line 280 runs through on-off switch 282 and unload speed potentiometer284 to servo controller 272 (also actuated by joystick 200). Now, lineon/off switch 268 is on (and switch 282 off) when combine 10 is not inan unloading mode, i.e., the combine is idle or harvesting grain. Switch282 is turned on (and switch 268 off) when the operator desires tooff-load grain from combine 10. In this manner, the operator can controlthe speed of vertical conveyor assembly 102 via motor 106. It will beappreciated that the function of switches 268 and 282 could be combinedinto a single switch unit.

When the operator desires to off-load grain from grain bin 28, theoperator also needs to control drag paddles 114/116 and belt 140. Thisis accomplished via on/off switch 281 (controlled by joystick 200) inline 283 that runs to solenoid-operated valve 284 that is disposed inline 286. Valve 284 is actuated by pump 288 that is powered by engine256 via line 290. Now, line 286 from valve 284 runs to hydraulic motor164, which runs belt 140, with the oil in line 286 returning to tank292. On/off switch 294 (also controlled by joystick 200) in line 295runs to solenoid-operated valve 293 that is disposed in line 291 thatbranches from line 286. Line 291 runs to hydraulic motor 118 that runsdrag paddles 114/116, with the oil returning to tank 292. At this pointin the description it should be noted that reservoir 224 is notated onthe drawings as the reservoir for all hydraulic fluid circuits.Obviously, additional reservoirs could be used as is necessary,desirable, or convenient.

The novel airbag suspension system now will be described with specificreference to FIGS. 21-23 for an endless track system; although, suchairbag suspension system can be adapted for tired wheels (see FIGS.24-27 and the description thereof and for a variety of articulatedvehicles (e.g., other farm vehicles, earth moving equipment (bulldozers, excavators, cranes), buses, mining equipment, etc.) in additionto combines. Endless track system 298 generally includes endlessmetallic sectioned or rubber traction belt 30 is seen to be mountedaround drive wheel 300 (wheel and hydraulic motor assembly) and idlerwheel 302. Additional intermediate idler wheels 304-312 are conventionalin use, location, and function, and generally ensure contact of track 30with the ground. Track system 298 is connected to frame member 314 ofgrain bin 28 (see FIG. 12) by stub axle 316. Another endless tracksystem 296 (see FIG. 23) is disposed opposite track system 298, but willnot be described in detail herein as it is a mirror image of tracksystem 298. Track system 296 is supported by frame 315 as seen in FIG.12.

Each track system 296/298 has a pair of airbag suspension systems, e.g.,318 and 320 airbag systems (nominal rating of, e.g., 10,000 pounds) fortrack system 298. Referring specifically to airbag system 320, airbag322 will be seen to be retained by upper plate member 324 that isconnected to frame member 314 and rests on lower plate assembly 326.Lower plate assembly 326 is connected to walking beam 328, which issupported by stub axle 316. Lower plate assembly 326 has a pair ofupstanding forward and rearward members, 330 and 332. Each upstandingmember 330/332 has a race or slot in which rides a cam follower, e.g.,cam follower 334 for upstanding member 330. Cam follower 334 (and theother cams not visible in the drawings) are connected to upper platemember 324 are free to move vertically, but are restrained from movinghorizontally. Thus, the cam followers dramatically reduce the largemoment in the axle caused by the tracks sliding as combine 10 turns.Note should be taken that while stub axle 316 can be located at thelongitudinal center of grain bin 28, it may be advantageous to locate itforward of such center of gravity so that grain bin 28 always is liftingup on joint 22. Also, walking beam 328 with its mounting only by stubaxle 316 permits about a 12 inch rise and fall of each of its ends,i.e., wheels 300 and 302 can move ±12 inches to accommodate uneventerrain.

The same type of airbag suspension system can be adapted for tiredwheels as was described for tracked wheels. Reference is made to FIG. 24in this regard whereat articulated combine 350 is shown to have itsrearward unit 352 supported by tired wheels 354 and 356 on one side, andon the other side by tired wheels 358 and 360 (see also FIGS. 25 and26). Each tired wheel 354/356/358/360 is separately powered by ahydraulic motor 362/364/366/368, respectively. Each forward tired wheelalso is designed to be turned about 15° by a hydraulic cylinderarrangement as seen in FIG. 26 wherein cylinder 394 is seen connectedfrom beam 384 to knuckle 396 for tired wheel 358 and cylinder 397 isseen connected from beam 382 to knuckle 398. Cylinders 394 and 397 arehydraulically actuated and can be integrated into the steering system ofcombine 10.

Tired wheels 356 and 358 are joined together by tie rod assembly 391,which connects knuckle 396 with knuckle 398. Tie rod assembly 391 passesthrough grain bin 28 at about its center, that is, where beams 382 and384 are attached to axles 378 and 380, respectively, in order tominimize the affect that the ups and downs that tired wheels 356 and 358would generate as combine 10 traversed over uneven ground. Finally,spring assemblies 393 and 395 are mounted in associated with tiredwheels 360 and 354, respectively, and bias tired wheels 360 and 354 to aneutral or straight-ahead configuration. Tired wheels 360 and 354 arepermitted to rotate slightly during a turn of combine 10 and springassemblies 393 and 395 return the wheels to a straight-ahead position.

The reason for permitting rear tired wheels 354 and 360 to “free-wheel”rotate slightly during a turning of front tired wheels 356 and 358 isdue to the geometry of turning an articulated vehicle. This can be seenby referring to FIG. 28 wherein an overhead simplified schematic ofcombine 350 is seen to include forward unit 351, having one set ofwheels, and rearward unit 352, have two pairs of wheels. Now, during aturn of articulated combine 350, each set of wheels must be on an arcthat meets at center 502 of the radius of the turn. The correspondingradii for each set of wheels are identified by radius 504 for the wheelsof forward unit 351, radius 506 for tired wheel 358, radius 508 fortired wheel 356, radius 510 for tired wheel 360, and radius 512 fortired wheel 354. One consequence of the turning geometry is permittingrear tired wheels 354 and 360 to rotate slightly to conform to theturning radius, with spring assemblies 393 and 395 biasing them backinto a straight position. Another consequence is that front tired wheels356 and 358 can be turned along the same radius and still an acceptableturning scheme would be present; although, their radii are slightlydifferent. Structuring a steering control system, then, accommodates theturning geometry illustrated in FIG. 28.

The airbag suspension system still is used; albeit in a slightlymodified condition. That is, airbags 370/372/374/376 are retained byframes and utilize cam follower assemblies, 386, 388, 390, and 392, asdescribed above. Stub axles 378 and 380 support walking beams 382 and384, respectively, which in turn support the airbag assemblies. Thus,each tired wheel 354/356/358/360 has the ability to rise and fall, forexample, ±12 inches, to accommodate uneven terrain. FIG. 27 illustratessuch construction in greater detail and taken in conjunction with FIG.26. The remainder of operation of articulated combine 350 is the same asdescribed above with respect to articulated combine 10.

Now, with respect to steering and controlling articulated combine 10,several unique problems are encountered. Prior art articulated vehiclestypically use hydraulic cylinders mounted across the articulation jointto produce steering force. The cylinders are controlled by a rotaryvalve mechanically connected to a steering wheel that is positioned bythe operator to achieve the desired turn or vehicle direction. Thissystem is used primarily on wheeled (tired) vehicles that have one axlein front of the joint and one behind the joint, such as an agriculturaltractor; or two axles behind the joint, such as a mining truck.Typically, the wheels on the axle, which are powered, are connectedtogether and receive power from a mechanical differential. Thedifferential permits a speed difference to be created between the twotired wheels which speed difference is required to turn with areasonable amount of force from the articulation cylinders. To initiatea turn in such an articulated vehicle, its also is necessary to slide orrotate the portion of the tires that are in contact with the ground orsupporting surface. This generally is feasible since the contact patchor portion of the tire diameter in contact with the supporting surfacegenerally is relatively small with respect to the diameter and width ofthe tires. Such tire sliding or rotating usually can be accomplishedwith a reasonable amount of force from the steering cylinders at thearticulation joint.

In an articulated combine wherein the rear module is supported byendless tracks powered by individual motors, such as is disclosed inapplication Ser. No. 09/210,331, cited above, the steering forces arequite different from the tired vehicle just described. The endlesstracks provide a much larger contact patch than do tires and, therefore,a much higher resistance to sliding or rotating them is encountered whena turn is initiated. The contact patch area also is elongated, whichfurther increases the force required from the articulation cylinders toinitiate a vehicle turn and to recover from a turn, which maneuver alsorequires sliding of the tracks laterally to position the vehicle in astraight alignment.

The steering forces are increased further when individual motors areused to power the tracks, rather than a single motor and a mechanicaldifferential to interconnect the two tracks. When individual motors oneach track are used, such motors typically receive hydraulic power froma common supply, whether such supply is one pump or two pumps that areinterconnected at their output ports. The common supply is necessary ina conventional system to ensure that the motors will share thepropulsion load since they are mechanically interconnected by thesupporting surface under the vehicle. The common supply provides thesame pressure to all motors, which means that each motor will producethe same torque or thrust when the system is in equilibrium and thevehicle is moving in a straight line. In order to initiate a turn, thesteering cylinders must provide sufficient force to change the arc oftravel of the tracks and establish an inside track and an outside trackrelationship that establishes a speed differential between the twotracks. The cylinders must overcome the natural tendency of the motorsto run at the same speed and to share equally the tractive effortrequired to move the vehicle. The cylinders must force an articulationangle that forces a portion of the tractive load to move to the insidetrack, which causes the pressure to go down in the outside track due toits mandated increase in speed. Hydraulic fluid flow to the outsidetrack motor increases immediately following the path of least resistanceuntil the pressure in the two motors equalizes. This process occurs anytime the articulation angle changes during a turn of the vehicle. Thesteering cylinders, therefore, must not only have sufficient force toslide or rotate the tracks, but also to create a backpressuredifferential between the two motors. The motors, thus, are resistingboth the initiation of a turn and a recovery from a turn.

The described problem can be reduced by using the differential steeringtechniques in conjunction with articulation cylinders as disclosed inapplication Ser. No. 09/210,331, cited above. An implementation of suchimproved technique is described below in connection with FIG. 29.

System Elements

A power source, which typically is an internal combustion enginedisposed in forward unit 12 and which drives hydraulic pumps, which inturn function as a controlled source of power for hydraulic motors andcylinders.

A support and tractive means on the front unit (e.g., wheel pair 20)powered by a hydraulic motor driving through a mechanical differential;although, use of individually driven tracks and tires can be used.

An articulation joint (e.g., articulation joint assembly 22) thatincludes at least one articulation cylinder and rod assembly (e.g.,hydraulic cylinder 46 or 48) to provide turning force wherein thecylinder is powered by a steering valve directing the flow from ahydraulic pump. The steering valve is controlled by the operator using asteering device, such as a wheel, or can be controlled by an automaticguidance system.

A support and tractive means for rearward unit 14 (e.g., endless trackassembly 298). Usually, there are two such track assemblies separatelyand independently powered by individual hydraulic motors, which receivepower from a pair of hydraulic pumps, each dedicated to a singlehydraulic motor. Each motor includes a transducer or sensor thatmeasures the rotational speed of the motor and provides that informationto a control system.

A programmable controller (e.g., CPU), which receives steering andpropulsion information from measurement transducers, performspreprogrammed or adaptive logic functions, and directs propulsion andsteering elements to implement the vehicle maneuvers commanded by theoperator or automatic guidance system.

An actuator, which receives commands form the programmable controllersand adjusts the output of the hydraulic pumps powering endless trackassembly 298 (and a similar assembly on the other side of rearward unit14) to cause the motors to execute the operator's desired vehiclemaneuvers. These actuators typically are digital stepping motors thatare adjusting the pump mechanism, which sets its output. In a typicalhydrostatic pump, this mechanism is called a swash plate, which sets thestroke of the pistons that determines the output flow of the pump.

System Characteristics

Motor speed is determined by the oil flow rate from the pump.

Motor torque is determined by the pressure applied to it up to thesetting on the relief valve, which opens at a preset pressure and allowshydraulic fluid to bypass the motor and flow back to the reservoir.

The load the motor is seeing at any point in time determines thepressure in the hydrostatic pump/motor loop. The swash plate in the pumpis establishing a flow rate to the motor. The pump will attempt toalways maintain that flow rate and the pressure rises or subsides asneeded to keep the motor rotating at a speed to accept that flow.

It is, therefore, possible to make multiple motors load share or accepta disproportionate share of the total system load by controlling thepressure of the hydraulic fluid flowing to them. This assumes thattraction will allow the load share or shift to occur, which dictates aspeed limiting control loop since the individual pumps are notcross-connected. If the motor is speeded up by increasing the pressureto it in order for the motor to take on a greater load and the trackpowered by such motor cannot achieve sufficient traction, the motor willoverspeed. The only controllable variable in the pump is flow bychanging the swash plate. However, motor pressure/torque/speed can becontrolled, assuming sufficient traction is available and the motor issized adequately to overcome the load placed on it, by controlling theflow of hydraulic fluid the pump is trying to force through it.

System Objectives

To cause the motors to share the forward or reverse propulsion loadwithin ±5% when the steering load on the articulation cylinders is lessthan a defined amount, say, 1,000 psi.

To assist the articulation cylinders to execute a turn whenever thecylinder pressure in either direction goes above 1,000 psi. Note: 1,000psi is exemplary, but based upon results of testing the articulatedtracked combine disclosed herein. Such figure may vary once furtheracceleration or starting on grade testing is undertaken. In thissituation, the pressure reference may not be as stable as speed andlikely will change with the load.

The foregoing system elements, characteristics, and objectives areembodied in FIG. 29. Specifically, inputs to micro-controller 400include left steering pressure signal 402 and right steering pressuresignal 404 from steering valve 406, which is actuated by the operatorrotating steering wheel 408. Signals 402/404 also are fed to leftarticulation cylinder 46 and right articulation cylinder 48 with lines410 and 412 supplying the necessary interconnection between cylinders46/48 and lines 410/412. Such interconnection is the primary steeringmechanism for articulated combine 10.

The operator indicates the desired speed of combine 10 through lever 414which is connected by line 416 to front axle pump 418 which drives frontmotor drive 420. Lines 422 and 424 interconnect pump 418 and motor 420with lines 426 and 428 providing two more inputs to controller 400.Potentiometer 430 provides a reference signal via line 432 to controller400. Left track pump 434 powers left track motor 436 via lines 438 and440, from which signals 442 and 444 are sent to controller 400. Line 446provides yet another input to controller 400 from left track motor 436.Right track pump 448 powers right track motor 450 via lines 452 and 454,from which signals 456 and 458 are sent to controller 400. Line 460provides yet another input to controller 400 from right track motor 436.Finally, controller 400 communicates with left track pump 434 via line462 and with right track pump 448 via line 464. All equipment isconventional in nature and design.

One condition that requires special attention for a tracked articulatedcombine is when the operator desires to commence movement (forward orreverse) from a standing or stop position with the steering wheel in aturning mode. Such initial turning movement requires tracks 30/32 toslide from rest, which requires a great amount of force/torque toovercome the consequent track friction with the ground. Theabove-described steering scheme can accommodate such conditions byinitiating the turn with the articulation cylinders augmented bypowering up only the outside track.

While combine 10 has been described as having non-steerable wheels, itshould be appreciated that combine 10 can be designed to have steerablefront wheels. Thus, steering of combine 10 can result from one or acombination of steerable forward unit wheels, articulation cylinders,and steerable (e.g., by speed differential or by wheel turning) rearwardtracks (or tired wheels).

Finally, it should be appreciated also that some and/or all of thehydraulic motors, valves, pumps, and the like, can be replaced bypneumatic motors and associated equipment, electric motors andassociated equipment, or by any other power generating device or system,so long as the design and operation remains with the precepts of thepresent invention.

While the invention has been described with reference to a preferredembodiment, those skilled in the art will understand that variouschanges may be made and equivalents may be substituted for elementsthereof without departing from the scope of the invention. In addition,many modifications may be made to adapt a particular situation ormaterial to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. In this application all units are in the metric system and allamounts and percentages are by weight, unless otherwise expresslyindicated. Also, all citations referred herein are expresslyincorporated herein by reference.

I claim:
 1. An airbag suspension for a vehicle, which comprises: (a) avehicle frame having an axle extending therefrom; (b) a longitudinalbeam affixed to said axle which carries at least one wheel; and (c) anairbag assembly comprising (i) an upper plate extending from saidvehicle frame (ii) a lower plate affixed to said longitudinal beam;(iii) an airbag disposed between said upper and lower plates; (v) a pairof vertical blocks having vertical slots, said blocks being carried bysaid lower plate; (vi) a pair of cams carried by said upper plate andriding in said vertical slots.
 2. The airbag suspension of claim 1,wherein said vehicle rides on a pair of endless tracks.
 3. The airbagsuspension of claim 1, wherein said vehicle rides on a pair of tiredwheels.
 4. The airbag suspension of claim 1, wherein each end of saidlongitudinal beam can move vertically about 24 inches.
 5. The airbagsuspension of claim 1, wherein said airbags are nominally rated at10,000 pounds.
 6. The airbag suspension of claim 1, wherein said vehicleis an articulated combine.
 7. The airbag suspension of claim 1, whereinsaid axle is a stub axle.